Update participants

PREPARATIONS.md

@@ -46,25 +46,26 @@ Confirmed:
 4. Rick de Leeuw
 5. Sake van Pelt
 6. Niels de Water
+7. Dirk Ages
+8. Arjen Langeveld
 
 Confirmed (but only if seats available):
 
 1. Magnus Palmblad
 2. Arzu Tugce Guler
-3. Dirk Ages
-4. Jonathan Vis
+3. Jonathan Vis
 
 Not yet confirmed (but with precedence):
 
 1. Saeed Katiraei
-2. Roel Zinkstok (ONCO)
-3. Tarek Malas
-4. Thomas Chin-A-Woeng
+2. Tarek Malas
+3. Thomas Chin-A-Woeng
 
 Cancelled:
 
 1. Johan den Dunnen
 2. Martijn Eenink
+3. Roel Zinkstok
 
 
 ## Course materials